Noncoking fuel injection nozzle

ABSTRACT

A fuel injection nozzle for internal combustion engines having an inwardly opening pressure operated valve positioned in a bore and guided for reciprocating movement in a guide of larger cross section than the stem of the valve wherein a hydraulic restriction to the reverse fuel flow between the stem and the bore is provided.

D United States Patent 1191 1111 Roosa Apr. 8, 1975 [54] NONCOKING FUELINJECTION NOZZLE 3.348.520 l0/l967 Lockwood 239/93 X {76] inventor:Vernon D. Roosa, c/o Hartford FOREIGN PATENTS OR APPUCATIONS Scre C 8 aga v 1.453.616 8/1966 France 239/533 Hartford. Conn. 06005 412.7412/l946 Italy 239/533 [22] Flled: 1967 Primary E.\'uminerLloyd L. King[2]] Appl. No.: 609,178 Attorney. Agent, or Firm-Prutzman. Hayes. Kalb &

Chilton [52] U.S. Cl. 239/533 1511 Int. Cl B05b 1/30 [57] I ABSTMCT [58]Field of Search 239/533, 87, 93 A fuel 1 for mmbusm" gines having aninwardly opening pressure operated [56] References cued valve positionedin a bore and guided for reciprocat- UNITED STATES PATENTS ing movementin a guide of larger cross section than 2 5 2 I I I 4/1 5 B h f 39, 33the stern of the valve wherein a hydraulic restriction to ISC O3.159.350 l2/l964 Mangold 239/533 lg 5 2? fuel flow between the Stem andthe bore 3.224.684 l2/1965 Roosa 239/533 p 3,255.974 6/1966 Roosu239/533 1 Claim, 4 Drawing Figures NONCOKING FUEL INJECTION NOZZLE Thisinvention relates generally to fuel injection nozzles for internalcombustion engines and to an improvement in the nozzle described in myprior U.S. Pat. No. 3,224,684 issued Dec. 21, 1965 and entitled FuelInjection Nozzle".

In fuel injection nozzles of the type contemplated by this invention,the plunger or valve is lifted from its seat by the pressure of the fueldelivered to the nozzle from an associated high pressure pump inmeasured quantities or charges. Each charge of fuel is discharged fromthe nozzle into a combustion chamber of an associated engine to operatethe engine at the desired speed and torque, and the discharge of thecharge from the nozzle is timed to take place when the air in thecombustion chamber is compressed and continues after ignition of thefuel begins. The nozzle incorporates a biasing spring to hold the valveagainst the valve seat and to reseat the valve after the charge isdischarged into the cylinder when the combustion pressure within thecylinder increases substantially. As the spring is reseating the valve,it is important that the pressure within the valve adjacent the seat issufficient to prevent combustion gases from entering the nozzle todeposit carbona ceous combustion products. A primary object of thisinvention is to provide a nozzle capable of preventing such entry ofcombustion gases.

Another object of this invention is to provide a nozzle capable ofmaintaining the pressure of the fuel within the nozzle adjacent thevalve seat at least equal to the combustion pressures within thecylinder during the closing of the valve.

Another object of this invention is to provide a nozzle constructed andarranged to provide differential hydraulic pressures between the inletand discharge ends of the nozzle sufficient to reseat the valve withoutthe reverse flow of combustion gases into the nozzle.

A still further object of this invention is to provide a fuel injectionnozzle in which the valve serves as a pump to provide a desired pressureof the fuel at the discharge end of the nozzle during the reseating ofthe valve.

Other objects will be in part obvious and in part pointed out more indetail hereinafter.

The invention accordingly consists in the features of construction,combination of elements and arrangement of parts which is exemplified inthe construction hereafter set forth, and the scope of the invention isindicated in the appended claims.

IN THE DRAWING FIG. I is a cross-sectional view of a portion of a fuelinjection nozzle embodying the present invention in conjunction with aschematic illustration of an associated high pressure pump fordelivering measured charges of fuel to the nozzle;

FIG. 2 is a cross-sectional view taken along lines 2-2 of FIG. 1;

FIG. 3 is a cross-sectional view taken along the lines 33 of FIG. 1; and

FIG. 4 is a cross-sectional view taken along the lines 4-4 of FIG. 1.

Referring to the drawing, in which like numerals refer to like partsthroughout the several views, the exemplary nozzle shown therein andembodying the present invention is generally similar to that illustratedin my aforementioned prior U.S. Pat. No. 3,224,684 and includes anelongated generally tubular body member 10, having a nozzle tip 12rigidly fixed at one end thereof, and a central longitudinal bore 14extending throughout its length. Located within the central bore 14 is arod-like plunger stem or valve 16 which cooperates with a valve seat 18formed in the nozzle tip 12 to control the discharge of fuel from thenozzle body I0. A valve guide 20 fixedly positioned within the bore 14of the body at a position remote from the valve seat I8 slidably mountsand precisely aligns the valve 16 so as to permit rapid reciprocalmovement thereof within the bore 14 under the influence of the fuelpressure within the bore 14 against the bias of spring 22. The nozzle isprovided with a fuel inlet 24 communicating with the bore 14 of thenozzle body 10 for delivery of high pressure fuel thereto adjacent theguide from an associated high pressure fuel pump 26.

The upper end of the valve 16 is provided with a partispherical surface25 which swivelly engages a spring seat 28 having a complementarypartispherical surface. The other end of the spring 22 is similarlyprovided with a spring seat 30 which swivelly engages an annular washer32 with the washer 32 and the spring seat 30 providing complementarypartispherical engaging surfaces to accommodate any lack of squarenessof the ends of the spring 22 or axial misalignment between the valve 16and the annular washer 32.

The annular washer 32 is seated against the end of an externally andinternally threaded longitudinally slotted retainer sleeve 34 theexternal threads 35 of which are threadably received in the internalmating threads 36 of the tubular body 10.

The internal threads 38 of retainer sleeve 34 threadably receive anexternally threaded pin 40 providing an adjustable lift stop for thevalve I6. With this arrangement, the nozzle valve opening pressure maybe adjusted as desired by merely turning the retainer sleeve 34 in orout until the desired biasing force is provided by the spring 22, andthe valve lift may be independently adjusted by axially adjusting thepin 40 with re spect to the retainer sleeve 34. Lock nut 46 which isthreaded on the external threads 35 of the retainer sleeve 34 istightened against the end shoulder 48 of the tubular body 10 to maintainthe retainer sleeve 34 and the lift stop pin 40 in adjusted position.

The charge pump 26 illustrated schematically in FIG. I is of the typemore fully described in my prior U.S. Pat. No. 3,204,622 issued Sept. 7,1965 and entitled Fuel Injection Pump Timing Device." It is sufficientto say for the purpose of describing this invention that the pump 26includes a pair of pistons 50 which are reciprocated radially as therotor 52 is rotated in timed relation with the associated engine throughintermediate roller shoes 54 and rollers 56 which engage diametricallyopposed cam lobes 58 of relatively stationary cam 60 to pressurize themeasured quantity or charge of fuel within the chamber 62 of the chargepump. As more fully explained in the aforesaid U.S. Pat. No. 3,204,622,the delivery passage 64 of pump 26 registers with the rotor outletpassage 65 from the charge pump chamber 62 to deliver the highlypressurized measured charge of fuel to inlet 24 of the charge pump.

The pressurized fuel delivered to the inlet 24 by the charge pumpincreases the pressure of the fuel within the bore 14 and acts on theareas 66 and 68 of the valve 16. When the force exerted thereby issufficient to overcome the bias of spring 22 to move the valve 16upwardly, the charge of fuel is discharged through the orifices in thenozzle tip 12.

As the rollers 56 begin to engage the trailing surface 580 of the camlobes 58, as shown in FIG. 1, the pressure within the passageway 64 andthe fuel inlet 24 of the nozzle rapidly reduces since very littlerestriction is offered to the flow of fuel therebetween.

The portion 16b (FIG. 3) of the valve 16 is shown as having a diameterwhich is less than that of guide portion 160 (FIG. 4). Thus, a drop ofpressure at the inlet 24 reduces the resultant hydraulic force acting onthe differential area of surface 66 over opposed area 67. Under suchconditions, the pressure in the chamber 140 acting on the area 68 andthe tip of the valve 16 becomes the dominating factor in the totalhydraulic force opposing the bias of spring 22.

In achieving the objectives of this invention, means forming a hydraulicrestriction effective to restrict the reverse flow of fuel from thechamber 140 to the inlet 24 are provided, In the exemplary embodiment,such a hydraulic restriction is provided by intentionally constructingand dimensioning the annular passageway between the portion l6b of thevalve and the bore 14 to effect a predetermined amount of restriction tothe reverse flow of fuel from the chamber 14a toward the fuel inlet 24during the reseating of the valve.

It will be further understood that during reseating the tip of the valve16 displaces a quantity of the fuel within the chamber 14a correspondingto the diameter of valve portion 16b multiplied by the longitudinalmovement of the valve 16 during reseating. Since the total hydraulicforce acting on surface 66 adjacent the inlet 24 and the tip of thevalve within chamber 140 are opposed by the spring 22, it will beapparent that as the spring reseats the valve, the valve acts as a pumpto pressurize the fuel in the chamber 140 at a level deter mined by therate of discharge of the fuel from cham ber 14a.

In the application of this concept to a specific nozzle structure havinga given spring force for spring 22 and given relative areas of portions16a and 16b of valve 16, the dimensions of the annular fuel passagewaybetween the chamber 140 and the inlet 24 may be so constructed andarranged to maintain or provide any desired fuel pressure in the chamber140 during the reseating of the valve by providing the desiredrestriction rate of flow from the chamber 14a to the inlet 24 dur ingreseating. In other words, with a given restriction to reverse fuel flowfrom chamber 140 to inlet 24, the valve 16 under the bias of spring 22serves as a pump to continue the pressure in the chamber 140 at any desired pressure until valve 16 is reseated. Where such pressure is equalto or greater than the effective cylinder pressures during the intervalof reseating of the valve 16, the entry of combustion gases into the tipof the valve adjacent the seat 18 is prevented.

In carrying out this invention, it is readily apparent that a number ofspecific combinations of dimensions could be utilized. One specificembodiment which has been constructed is as follows:

Diameter of guide portion [6a 0126:: Diameter of stem portion 16b 0.080Diameter of bore 14 (1105 Diameter of valve seat l3 0.060" Approximatelength of uniform re -Continued stricted passage between bore l4 andstem [6b (FIG. 3) 2.5" Spring force 27 No.

With the nozzle having the foregoing dimensions, a pressure of just over2800 psi. will be required to initially open the nozzle when usingconventional diesel fuel under normal room temperature conditions. Whenthe rollers 56 begin to descent the trailing surface of cam lobes 58 ofpump 26 and the pressure at the inlet 24 drops to, say, 2000 p.s.i., thespring 22 will move the valve toward the valve seat 18 and maintain ahydraulic pressure in the chamber 14a at the nozzle tip at slightly morethan 2400 psi. Since this pressure is well above the typical maximumeffective combustion pressure of 1500 psi. developed in conventionalcommercially available nonsupercharged diesel engines, it is readilyapparent, and test results confirm, that the nozzle will not permitcombustion gases to enter the discharge orifices of the nozzle. Statedanother way, by providing a hydraulic restriction effective to restrictthe flow of fuel from the chamber 14a at the nozzle tip to the inlet 24as the pressure at inlet 24 is falling, the pressure in the chamber 14amay be maintained at a higher level than cylinder pressure during thereseating of valve 16 to prevent combustion gases from entering thedischarge orifices of the nozzle. This eliminates the possibility ofdeposits of tacky and tar-like carbonaceous components of the gaseswithin the nozzle and on the valve seat.

From the foregoing it is apparent that this invention provides a fuelnozzle which will prevent the entry of combustion gases into the nozzleby maintaining the pressure of the fuel in the nozzle adjacent thenozzle tip at the desired level until the valve is fully reseated underthe influence of the biasing spring.

As will be apparent to persons skilled in the art, vari ousmodifications and adaptations of the structure above-described willbecome readily apparent without departure from the spirit and scope ofthe invention, the scope of which is defined in the appended claims.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as fol lows:

1. In the operation of an inwardly opening pressure actuated nozzlehaving a plunger normally biased against a valve seat to close the same,a chamber ad jacent the valve seat, and an inlet for receivingintermittent pulses of high pressure fuel for delivery through a passagein the nozzle communicating with said chamber, the steps of delivering apulse of fuel under high pressure to the inlet to apply a hydraulicforce on the plunger sufficient to lift the plunger from the valve seatagainst the normal bias thereon and to discharge the fuel through thevalve seat and maintaining, until the plunger is fully seated, thepressure in said chamber at a level substantially equal to the pressuretherein when the plunger begins to reseat by restricting the reverseflow of fuel in said passage as the normal bias exceeds the hydraulicforce on said plunger toward the end of the delivery of the pulse.

1. In the operation of an inwardly opening pressure actuated nozzle having a plunger normally biased against a valve seat to close the same, a chamber adjacent the valve seat, and an inlet for receiving intermittent pulses of high pressure fuel for delivery through a passage in the nozzle communicating with said chamber, the steps of delivering a pulse of fuel under high pressure to the inlet to apply a hydraulic force on the plunger sufficient to lift the plunger from the valve seat against the normal bias thereon and to discharge the fuel through the valve seat and maintaining, until the plunger is fully seated, the pressure in said chamber at a level substantially equal to the pressure therein when the plunger begins to reseat by restricting the reverse flow of fuel in said passage as the normal bias exceeds the hydraulic force on said plunger toward the end of the delivery of the pulse. 